https://github.com/ReactiveX/RxJava: Reactive Extensions for Java
  • David Karnok 
Copyright (c) 2016-present, RxJava Contributors.
Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
compliance with the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software distributed under the License is
distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
the License for the specific language governing permissions and limitations under the License.

/**
 * Copyright (c) 2016-present, RxJava Contributors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in
 * compliance with the License. You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is
 * distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See
 * the License for the specific language governing permissions and limitations under the License.
 */

package io.reactivex.internal.operators.observable;

import java.util.*;
import java.util.concurrent.Callable;
import java.util.concurrent.atomic.*;

import io.reactivex.ObservableSource;
import io.reactivex.Observer;
import io.reactivex.disposables.*;
import io.reactivex.exceptions.Exceptions;
import io.reactivex.functions.Function;
import io.reactivex.internal.disposables.DisposableHelper;
import io.reactivex.internal.functions.ObjectHelper;
import io.reactivex.internal.queue.SpscLinkedArrayQueue;
import io.reactivex.internal.util.AtomicThrowable;
import io.reactivex.plugins.RxJavaPlugins;

public final class ObservableBufferBoundary<T, U extends Collection<? super T>, Open, Close>
extends AbstractObservableWithUpstream<T, U> {
    final Callable<U> bufferSupplier;
    final ObservableSource<? extends Open> bufferOpen;
    final Function<? super Open, ? extends ObservableSource<? extends Close>> bufferClose;

    public ObservableBufferBoundary(ObservableSource<T> source, ObservableSource<? extends Open> bufferOpen,
                                    Function<? super Open, ? extends ObservableSource<? extends Close>> bufferClose, Callable<U> bufferSupplier) {
        super(source);
        this.bufferOpen = bufferOpen;
        this.bufferClose = bufferClose;
        this.bufferSupplier = bufferSupplier;
    }

    @Override
    protected void subscribeActual(Observer<? super U> t) {
        BufferBoundaryObserver<T, U, Open, Close> parent =
            new BufferBoundaryObserver<T, U, Open, Close>(
                t, bufferOpen, bufferClose, bufferSupplier
            );
        t.onSubscribe(parent);
        source.subscribe(parent);
    }

    static final class BufferBoundaryObserver<T, C extends Collection<? super T>, Open, Close>
    extends AtomicInteger implements Observer<T>, Disposable {

        private static final long serialVersionUID = -8466418554264089604L;

        final Observer<? super C> downstream;

        final Callable<C> bufferSupplier;

        final ObservableSource<? extends Open> bufferOpen;

        final Function<? super Open, ? extends ObservableSource<? extends Close>> bufferClose;

        final CompositeDisposable observers;

        final AtomicReference<Disposable> upstream;

        final AtomicThrowable errors;

        volatile boolean done;

        final SpscLinkedArrayQueue<C> queue;

        volatile boolean cancelled;

        long index;

        Map<Long, C> buffers;

        BufferBoundaryObserver(Observer<? super C> actual,
                ObservableSource<? extends Open> bufferOpen,
                Function<? super Open, ? extends ObservableSource<? extends Close>> bufferClose,
                Callable<C> bufferSupplier
        ) {
            this.downstream = actual;
            this.bufferSupplier = bufferSupplier;
            this.bufferOpen = bufferOpen;
            this.bufferClose = bufferClose;
            this.queue = new SpscLinkedArrayQueue<C>(bufferSize());
            this.observers = new CompositeDisposable();
            this.upstream = new AtomicReference<Disposable>();
            this.buffers = new LinkedHashMap<Long, C>();
            this.errors = new AtomicThrowable();
        }

        @Override
        public void onSubscribe(Disposable d) {
            if (DisposableHelper.setOnce(this.upstream, d)) {

                BufferOpenObserver<Open> open = new BufferOpenObserver<Open>(this);
                observers.add(open);

                bufferOpen.subscribe(open);
            }
        }

        @Override
        public void onNext(T t) {
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                for (C b : bufs.values()) {
                    b.add(t);
                }
            }
        }

        @Override
        public void onError(Throwable t) {
            if (errors.addThrowable(t)) {
                observers.dispose();
                synchronized (this) {
                    buffers = null;
                }
                done = true;
                drain();
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void onComplete() {
            observers.dispose();
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                for (C b : bufs.values()) {
                    queue.offer(b);
                }
                buffers = null;
            }
            done = true;
            drain();
        }

        @Override
        public void dispose() {
            if (DisposableHelper.dispose(upstream)) {
                cancelled = true;
                observers.dispose();
                synchronized (this) {
                    buffers = null;
                }
                if (getAndIncrement() != 0) {
                    queue.clear();
                }
            }
        }

        @Override
        public boolean isDisposed() {
            return DisposableHelper.isDisposed(upstream.get());
        }

        void open(Open token) {
            ObservableSource<? extends Close> p;
            C buf;
            try {
                buf = ObjectHelper.requireNonNull(bufferSupplier.call(), "The bufferSupplier returned a null Collection");
                p = ObjectHelper.requireNonNull(bufferClose.apply(token), "The bufferClose returned a null ObservableSource");
            } catch (Throwable ex) {
                Exceptions.throwIfFatal(ex);
                DisposableHelper.dispose(upstream);
                onError(ex);
                return;
            }

            long idx = index;
            index = idx + 1;
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                bufs.put(idx, buf);
            }

            BufferCloseObserver<T, C> bc = new BufferCloseObserver<T, C>(this, idx);
            observers.add(bc);
            p.subscribe(bc);
        }

        void openComplete(BufferOpenObserver<Open> os) {
            observers.delete(os);
            if (observers.size() == 0) {
                DisposableHelper.dispose(upstream);
                done = true;
                drain();
            }
        }

        void close(BufferCloseObserver<T, C> closer, long idx) {
            observers.delete(closer);
            boolean makeDone = false;
            if (observers.size() == 0) {
                makeDone = true;
                DisposableHelper.dispose(upstream);
            }
            synchronized (this) {
                Map<Long, C> bufs = buffers;
                if (bufs == null) {
                    return;
                }
                queue.offer(buffers.remove(idx));
            }
            if (makeDone) {
                done = true;
            }
            drain();
        }

        void boundaryError(Disposable observer, Throwable ex) {
            DisposableHelper.dispose(upstream);
            observers.delete(observer);
            onError(ex);
        }

        void drain() {
            if (getAndIncrement() != 0) {
                return;
            }

            int missed = 1;
            Observer<? super C> a = downstream;
            SpscLinkedArrayQueue<C> q = queue;

            for (;;) {
                for (;;) {
                    if (cancelled) {
                        q.clear();
                        return;
                    }

                    boolean d = done;
                    if (d && errors.get() != null) {
                        q.clear();
                        Throwable ex = errors.terminate();
                        a.onError(ex);
                        return;
                    }

                    C v = q.poll();
                    boolean empty = v == null;

                    if (d && empty) {
                        a.onComplete();
                        return;
                    }

                    if (empty) {
                        break;
                    }

                    a.onNext(v);
                }

                missed = addAndGet(-missed);
                if (missed == 0) {
                    break;
                }
            }
        }

        static final class BufferOpenObserver<Open>
        extends AtomicReference<Disposable>
        implements Observer<Open>, Disposable {

            private static final long serialVersionUID = -8498650778633225126L;

            final BufferBoundaryObserver<?, ?, Open, ?> parent;

            BufferOpenObserver(BufferBoundaryObserver<?, ?, Open, ?> parent) {
                this.parent = parent;
            }

            @Override
            public void onSubscribe(Disposable d) {
                DisposableHelper.setOnce(this, d);
            }

            @Override
            public void onNext(Open t) {
                parent.open(t);
            }

            @Override
            public void onError(Throwable t) {
                lazySet(DisposableHelper.DISPOSED);
                parent.boundaryError(this, t);
            }

            @Override
            public void onComplete() {
                lazySet(DisposableHelper.DISPOSED);
                parent.openComplete(this);
            }

            @Override
            public void dispose() {
                DisposableHelper.dispose(this);
            }

            @Override
            public boolean isDisposed() {
                return get() == DisposableHelper.DISPOSED;
            }
        }
    }

    static final class BufferCloseObserver<T, C extends Collection<? super T>>
    extends AtomicReference<Disposable>
    implements Observer<Object>, Disposable {

        private static final long serialVersionUID = -8498650778633225126L;

        final BufferBoundaryObserver<T, C, ?, ?> parent;

        final long index;

        BufferCloseObserver(BufferBoundaryObserver<T, C, ?, ?> parent, long index) {
            this.parent = parent;
            this.index = index;
        }

        @Override
        public void onSubscribe(Disposable d) {
            DisposableHelper.setOnce(this, d);
        }

        @Override
        public void onNext(Object t) {
            Disposable upstream = get();
            if (upstream != DisposableHelper.DISPOSED) {
                lazySet(DisposableHelper.DISPOSED);
                upstream.dispose();
                parent.close(this, index);
            }
        }

        @Override
        public void onError(Throwable t) {
            if (get() != DisposableHelper.DISPOSED) {
                lazySet(DisposableHelper.DISPOSED);
                parent.boundaryError(this, t);
            } else {
                RxJavaPlugins.onError(t);
            }
        }

        @Override
        public void onComplete() {
            if (get() != DisposableHelper.DISPOSED) {
                lazySet(DisposableHelper.DISPOSED);
                parent.close(this, index);
            }
        }

        @Override
        public void dispose() {
            DisposableHelper.dispose(this);
        }

        @Override
        public boolean isDisposed() {
            return get() == DisposableHelper.DISPOSED;
        }
    }
}